This invention relates to a vehicle movement stabilizing device for stabilizing the movement of a traveling vehicle during braking, accelerating or turning by controlling frictional force adding means for increasing the frictional force of the wheels or vehicle to the road surface, and reliably carrying out the stabilizing control.
A traveling vehicle is operated by carrying various movements such as braking, acceleration and turning according to the condition of the road surface by operating the brakes, accelerator and steering wheel. For any movement, it is a prerequisite that the friction coefficient μ of the wheels to the road surface is a normal value (high-μ road) such as on an asphalt road, and stable travel is ensured by the braking action by a brake device (first braking device) for applying brakes to the rotation of the wheels. Among actual road surfaces, there are low-μ roads where the value of μ is extremely small, such as frozen roads, on which it is impossible to achieve stable travel because of insufficient braking operation by the first braking device.
Thus, besides the first braking device, means is desired which can add the frictional force by some means. As such means, one is means which increase the friction coefficient μ of the wheels to the road surface, and another is means which impart frictional force of the vehicle to the road surface. As the former means, spike tires have been proposed and embodied. But because spike tires abrade roads and cause dust pollution, they are prohibited now. Also, a so-called ABS (antilock brake system) is widely known as a system which efficiently carries out braking of wheels by recovering the frictional coefficient as much as possible by interrupting braking at short intervals. But sufficient braking force was sometimes not obtained because the value μ is extremely small on frozen roads.
As a measure to directly increase the friction coefficient μ, a slip preventive assisting device is proposed by JP patent publication 8-25905 (publication 1). In this publication 1, a slip preventive assisting device is disclosed in which because dust pollution and environmental pollution occur if sand is scattered to prevent slip, slip preventive particles such as ice particles are scattered together with water to increase the friction coefficient μ so that slip can be prevented without pollution.
As a means which can add frictional force to the wheel even if the friction coefficient μ is small, an emergency brake device is proposed in JP patent publication 8-156760 (publication 2). In the device of publication 2, a second braking means comprising a friction material which can directly engage the road surface and a hydraulic cylinder for operating the friction material is provided. If detection is made that the friction coefficient μ of the road surface is so small as to fall into a slip state by normal braking, the second braking means is activated to put the friction material into engagement with the road surface to impart frictional force to the vehicle.
With the slip preventive device of publication 1, it is possible to increase the friction coefficient μ between the tires and the road surface by scattering slip preventive particles. With the emergency braking device, too, it is possible to obtain frictional force of the vehicle to the road surface by pressing and engaging the friction plate against the road surface. Thus, the device of either publication can achieve shortening of the braking distance. But in either of the devices of publications 1 and 2, while description is made about shortening the braking distance by applying effective braking to the vehicle, no mention is made whatsoever about how braking, acceleration and turning movements are controlled using the respective devices during braking, acceleration and turning of the vehicle, or how the operation is reliably finished by checking the end.
With a vehicle having the emergency brake device of publication 2, when stopping the vehicle, the driver manually presses the reset button to finish the operation. Thus, it is inferior in convenience.
An object of this invention is to provide a vehicle movement stabilizing device in which in effectively functioning braking, acceleration and turning movement during travel of the vehicle by activating frictional force adding means to achieve stability of travel, start and end of the activation of the frictional force adding means are controlled so as to be carried out automatically, reliably and suitably, while preventing repetition of unnecessary operations.